Workpiece Processing Technique

ABSTRACT

Methods for processing of a workpiece are disclosed. The actual rate at which different portions of an ion beam can process a workpiece, referred to as the processing rate profile, is determined by measuring the amount of material removed from, or added to, a workpiece by the ion beam as a function of ion beam position. An initial thickness profile of a workpiece to be processed is determined. Based on the initial thickness profile, a target thickness profile, and the processing rate profile of the ion beam, a first set of processing parameters are determined. The workpiece is then processed using this first set of processing parameters. In some embodiments, an updated thickness profile is determined after the first process and a second set of processing parameters are determined. A second process is performed using the second set of processing parameters. Optimizations to improve throughput are also disclosed.

-   Embodiments of the present disclosure relate to a method of    selectively processing a workpiece, and more particularly, to    selectively performing an etch, deposition or amorphization process    on a semiconductor workpiece.

BACKGROUND

Improvement in yields for semiconductor devices is a continuous goal.One area that may be improved is uniformity control across theworkpiece. In certain processes, the workpiece may receive moretreatment in one region, such as near the center of the workpiece, thanin other regions.

For example, a deposition process may deposit more material near thecenter of a workpiece than near the outer edge of that workpiece. Thismay be due to the increased plasma density near the center of thedeposition chamber.

In another example, a spin coating process may leave more material nearthe outer edge of the workpiece, as compared to the center of theworkpiece. This may be due to the centripetal force pushing the coatingtoward the outer edge of the workpiece.

In each of these examples, this process non-uniformity may negativelyimpact the yield of a semiconductor workpiece. In some cases, effortsare made to improve the uniformity of the process. However, there may belimits to the degree of uniformity that may be achieved.

For example, the ion beam used to process the semiconductor workpiece tocorrect this non-uniformity may itself be non-uniform. Thisnon-uniformity of the ion beam may result in different processing ratesof the workpiece. There are some techniques that may be used to attemptto measure and quantify or correct the uniformity of an ion beam.However, the granularity of such tools may not be sufficient for theseselective area processes. Further, the process may not be directlyrelated to ion beam current. For example, the background gas levels ofspecies, such as oxygen, may change the etch, amorphization ordeposition rates. Therefore, it would be beneficial if there were amethod of more precisely quantifying the rate at which differentportions of an ion beam can process a workpiece, and using thisinformation to subsequently process one or more workpieces. Further, itwould be advantageous if this quantification did not affect thethroughput of the processing equipment.

SUMMARY

Methods for processing of a workpiece are disclosed. The actual rate atwhich different portions of an ion beam can process a workpiece,referred to as the processing rate profile, is determined by measuringthe amount of material removed from, or added to, a workpiece by the ionbeam as a function of ion beam position. Subsequently, an initialthickness profile of a workpiece to be processed is determined. Based onthe initial thickness profile, a target thickness profile, and theprocessing rate profile of the ion beam, a first set of processingparameters are determined. The workpiece is then processed using thisfirst set of processing parameters. In some embodiments, an updatedthickness profile is determined after the first process and a second setof processing parameters are determined based on the updated thicknessprofile, the target thickness profile and the processing rate profile ofthe ion beam. A second process is performed using the second set ofprocessing parameters. Optimizations to improve throughput are alsodisclosed.

According to one embodiment, a method of processing a workpiece isdisclosed. The method comprises measuring an initial thickness profileof a first workpiece; directing an ion beam toward the first workpiecefor a predetermined time or dose; measuring an updated thickness profileof the first workpiece after the directing; determining an etch rateprofile of the ion beam as a function of ion beam position based on adifference between the initial thickness profile and the updatedthickness profile; and processing a second workpiece based on the etchrate profile of the ion beam. In some embodiments, the processing of thesecond workpiece is performed using a plurality of passes, wherein theion beam is scanned across the second workpiece during each pass,wherein the etch rate profile is used to determine a first set ofprocessing parameters that are selected from the group consisting of anumber of passes, and operating parameters used during each pass. Theoperating parameters may be selected from the group consisting of a scanspeed profile, a duty cycle of the ion beam, an extraction current orvoltage, and a pressure of a feed gas. In certain embodiments, theinitial thickness profile and the updated thickness profile are measuredusing a reflectometer. The processing of the second workpiece maycomprise an etch process, a deposition process or an amorphizationprocess.

According to a second embodiment, a method of processing a workpiece isdisclosed. The method comprises determining a processing rate profile ofan ion beam as a function of ion beam position; determining an initialthickness profile of the workpiece; using the processing rate profile,the initial thickness profile and a target thickness profile tocalculate a first set of processing parameters; and processing theworkpiece using the first set of processing parameters. In certainembodiments, the method further comprises determining an updatedthickness profile of the workpiece after the processing; using theprocessing rate profile, the updated thickness profile and the targetthickness profile to calculate a second set of processing parameters;and processing the workpiece using the second set of processingparameters. In some embodiments, the processing rate profile isdetermined by measuring an initial thickness profile of a sacrificialworkpiece; directing the ion beam toward the sacrificial workpiece for apredetermined time or dose; measuring an updated thickness profile ofthe sacrificial workpiece after the directing; and determining theprocessing rate profile based on a difference between the initialthickness profile and the updated thickness profile. In certainembodiments, the processing rate profile comprises an etch rate profile.In other embodiments, the processing rate profile comprises a depositionrate profile.

According to a third embodiment, a method of processing a plurality ofworkpieces from a lot is disclosed. The method comprises determining anetch rate profile of an ion beam as a function of ion beam positionusing a sacrificial workpiece; determining an initial thickness profileof a first workpiece of the lot; using the etch rate profile, theinitial thickness profile of the first workpiece and a target thicknessprofile to calculate a first set of processing parameters; processingthe first workpiece of the lot using the first set of processingparameters; and processing a second workpiece of the lot using the firstset of processing parameters. In certain embodiments, the method furthercomprises, before processing the second workpiece, determining anupdated thickness profile of the first workpiece of the lot after theprocessing of the first workpiece; using the etch rate profile, theupdated thickness profile of the first workpiece and the targetthickness profile to calculate a second set of processing parameters forthe first workpiece; and processing the first workpiece of the lot usingthe second set of processing parameters for the first workpiece. Incertain embodiments, the method further comprises determining an updatedthickness profile of the second workpiece of the lot after processingthe second workpiece; using the etch rate profile, the updated thicknessprofile of the second workpiece and the target thickness profile tocalculate a second set of processing parameters for the secondworkpiece; and processing the second workpiece of the lot using thesecond set of processing parameters for the second workpiece.

BRIEF DESCRIPTION OF THE FIGURES

For a better understanding of the present disclosure, reference is madeto the accompanying drawings, which are incorporated herein by referenceand in which:

FIG. 1 is a representative ion implantation system;

FIG. 2 shows a flowchart that may be used to determine processing rateprofile of an ion beam;

FIG. 3 is a representative etch rate profile calculated using thesequence shown in FIG. 2;

FIG. 4 shows a flowchart that may be used to process a workpiece; and

FIG. 5 shows a flowchart that may be used to process a lot ofworkpieces.

DETAILED DESCRIPTION

As described above, processes are often non-uniform, leading todifferent characteristics across the semiconductor workpiece. Further,in certain processes, elimination of this non-uniformity may bedifficult. For example, deposition processes may deposit more materialon certain portions of a workpiece, such as near the center, due toincreased plasma density in this region. Creation of a plasma that iscompletely uniform across the workpiece may be challenging.

In certain embodiments, the uniformity of the workpiece may be improvedby performing a selective process. For example, it may be desirable tocreate a workpiece that has a thickness that is constant across theworkpiece to within a predetermined tolerance. To achieve this, aworkpiece having a known thickness profile may be subjected to aselective etching process to remove material from the workpiece untilthe thickness across the workpiece is within a predetermined tolerance.In other embodiments, the uniformity of the workpiece may be improved byperforming a selective deposition process, or a selective amorphizationprocess.

Ion beams are often used to perform these processes. In the case of anetching process, exposure of a workpiece to an ion beam of a particularspecies may remove material from the workpiece. However, the rate atwhich the material is removed, also referred to as etch rate, may varyacross the workpiece. This may be due to a number of factors. Forexample, the etch rate is related to the ion beam current; however, theion beam itself may not be uniform. Regions of the workpiece that areexposed to higher current portions of the ion beam may be etched at ahigher rate than other regions. Further, the etch rate may also be afunction of the composition of the workpiece and the species used tocreate the ion beam. Other factors may also affect the etch rate of aworkpiece. For example, the background gas levels of species, such asoxygen, may change the etch rate. Similarly, the deposition andamorphization rates may also vary based on ion beam current, the speciesthat is being deposited and other factors.

FIG. 1 shows an illustrative schematic of an ion implanter 100. The ionimplanter 100 includes an ion source 110, which is used to create ionsfrom one or more feed gasses. Ions are extracted from the ion source110, typically through the use of electrically biased electrodes 120disposed proximate an extraction aperture on the ion source 110. Theextracted ions are then manipulated by a series of beam line components130, which shape and focus the ion beam 140. The beam line componentsmay include accelerators, decelerators, mass analyzers and collimatingmagnets. The ion beam 140 may be a ribbon beam, where one dimension ofthe ion beam 140 is much greater than the other dimension. In anotherembodiment, the ion beam 140 may be a spot beam, which may be nearlycircular in shape.

The ion beam 140 is then directed toward a workpiece 10, which may beclamped to a platen 150. The platen 150 may be capable of movement inthe horizontal, vertical and rotational directions.

To process the workpiece 10, the ion beam 140 may be directed toward theworkpiece 10. The platen 150 may then be translated in multipledirections to allow the ion beam 140 to impact the various regions ofthe workpiece 10.

An optical system, such as a reflectometer 160, may be used to determinethickness of workpieces 10. Information from the reflectometer 160 maybe used by a controller 170 to adjust the parameters of the ion source110, or the platen 150. The controller 170 includes a processing unit171 used in conjunction with a storage element 172. The storage element172 may contain non-transitory media that is used to store instructionsthat may be executed by the processing unit 171. Thus, the controller170 may be capable of performing the sequences described herein.

In certain embodiments, material is removed from a workpiece to create aworkpiece having the targeted thickness profile. In this embodiment, ionimplanter 100 may be used to selectively remove material from theworkpiece 10. The determination of the amount of material that is to beremoved from the workpiece 10 may be made by the controller 170, basedon the initial thickness profile of the workpiece 10 and the targetthickness profile. The initial thickness profile of the workpiece 10 maybe determined using the reflectometer 160. The target thickness profilemay be a known quantity that is input to the controller 170. Thiscalculation results in a three dimensional map, where each location onthe workpiece is represented in two dimensions, such as (x,y), and thethickness to be deposited or removed from that location is the value atthat location. This matrix may be referred to as the materialmodification matrix and may be stored in the storage element 172 of thecontroller 170. In the case of an etching process, this matrix mayrepresent the amount of material to be removed from each location on theworkpiece. Alternatively, in the case of a deposition process, thismatrix may represent the amount of material to be deposited on eachlocation on the workpiece.

The actual etch rate of the material as a function of ion beam positionmay be used on conjunction with the material modification matrix by thecontroller 170 to determine the processing parameters that are to beused to process the workpiece 10. For example, during the processing,the workpiece 10 may be subjected to a plurality of passes of the ionbeam 140. During each pass, the ion beam 140 scans the entire workpiece10 or a portion thereof. The speed of the platen 150 relative to the ionbeam 140 may vary during the scan to allow certain portions of theworkpiece 10 to be processed more than other portions. In certainembodiments, multiple passes are performed. For example, a first passmay be performed by moving the ion beam 140 from the top of theworkpiece 10 to the bottom of the workpiece 10 in a vertical direction.After this first pass is completed, the workpiece may be rotated by360/N degrees by the platen 150, where N is the number of passes thatare to be performed. After the rotation is complete, the ion beam 140may again scan from the top of the workpiece 10 to the bottom of theworkpiece 10, or from the bottom of the workpiece 10 to the top of theworkpiece 10. This is repeated until all N passes are performed. Asnoted above, the speed of each pass may vary. Additionally, oralternatively, the beam current may be modified by varying the dutycycle of the ion beam, or the extraction current or voltage.Additionally or alternatively, another operating parameter, such aspressure of the feed gas, or distance between the platen and the ionsource, may vary for each pass and/or rotation. Further, the speed andother operating parameters may vary during each individual pass. Thenumber of passes, and the scan speed profile during each pass and theother operating parameters used during each pass may be determined bythe controller 170.

Calculating a etch rate may be done indirectly. For example, the beamcurrent of the ion beam can be determined and this value can be used todetermine the expected etch rate. In the present disclosure, the rate atwhich the workpiece is processed due to the ion beam, also referred toas processing rate profile, is measured directly.

FIG. 2 shows a process that may be used to determine the actual etchrate profile of an ion beam as a function of ion beam position. Thisprocess may be performed using controller 170, or may use a differentcontroller. First, as shown in Process 200, the thickness profile of theworkpiece 10 is determined. This may be performed using thereflectometer 160, which scans across the workpiece 10. Based on thetime difference between the transmitted light and the reflected light,the initial thickness profile of the workpiece 10 may be determined. Thereflectometer 160 may be used to determine the thickness of theworkpiece 10 at a plurality of locations. For example, in oneembodiment, a thickness measurement may be performed every 0.5 mm inboth directions. This yields a three dimensional array, defined as thetwo dimensional position on the workpiece and the thickness of theworkpiece at that two dimensional location.

Then, as shown in Process 210, the ion beam 140 is then directed towardthe workpiece 10. During this time, the ion beam 140 is not scannedrelative to the workpiece 10. Rather, the ion beam 140 remainsstationary relative to the workpiece 10 for a predetermined time or apredetermined dose. After the predetermined time or dose, the ion beam140 is disabled, as shown in Process 220. In Process 230, the thicknessprofile of this processed workpiece is then determined, using thetechnique described above in Process 200.

The processed thickness profile is then subtracted from the initialthickness profile to yield the actual etch rate profile, as shown inProcess 240. Thus, the etch rate profile is determined based on thedifference between the initial thickness profile and the processedthickness profile. An example of an actual etch rate profile is shown inFIG. 3. This figure shows the effect of the ion beam 140, as a functionof ion beam position, on the workpiece 10. The x-axis is along the longdimension of the ion beam 140, which may be a ribbon beam, and isreferenced to the center of the ion beam 140. Thus, the x-axis iscentered at 0. The y-axis is along the short dimension of the ribbonbeam and is similarly referenced to the center of the ion beam 140. Thez-axis is indicative of the amount of material removed from theworkpiece 10 by the ion beam 140 during Process 210. In certainembodiments, the z-axis represents the actual amount of material,measured in angstroms, that was removed from the workpiece 10 in Process210. In other embodiments, the z-axis may represent an etch rate,measured in thickness per unit time, or angstroms/sec. For example, thez-axis may represent the actual amount of material removed, measured inangstroms, divided by the predetermined time used in Process 210.

Note that the ion beam 140 creates a non-uniform pattern in theworkpiece 10. For example, in this example, the center of the ion beam140, referred to as (0,0) in FIG. 3, etches far more material from theworkpiece 10 than other portions of the ion beam 140. The profile ofFIG. 3 may be generated by taking a plurality of scans using areflectometer, where each scan may be performed 0.5 mm from the previousscan. This plurality of scans is then processed to form the etch rateprofile shown in FIG. 3.

If the actual etch rate of the ion beam, as a function of ion beamposition, is known, selective processing of a workpiece may beperformed. FIG. 4 shows a processing sequence that may be used toselectively process a workpiece. This process may be performed usingcontroller 170. First, as shown in Process 400, the actual etch rateprofile of the ion beam is determined empirically using a sacrificialworkpiece. In other embodiments, the actual etch rate profile isdetermined using the workpiece to be processed. This may be done usingthe sequence shown in FIG. 2.

Next, the initial thickness profile of a workpiece 10 to be processed ismeasured, as shown in Process 410. Based on this initial thicknessprofile and the target thickness profile (which may be input to thecontroller 170), a first material modification matrix may be generated,as shown in Process 420. As described above, the first materialmodification matrix is the difference between the initial thicknessprofile of the workpiece 10 and the target thickness profile. This firstmaterial modification matrix may be stored in the storage element 172.The first material modification matrix is used to determine the amountof material to remove or deposit to each location on the workpiece 10.

Based on the first material modification matrix and the actual etch rateprofile of the ion beam, a first set of processing parameters may bedetermined by the controller 170, as shown in Process 430. This firstset of processing parameters includes the number of passes that are tobe performed, as well as the scan speed profile and operating parametersto be used during each pass. For example, if the first materialmodification matrix indicates that more material is to be removed in aspecific region of the workpiece, one or more of the passes may slow thescan speed when this region of the workpiece is exposed to the ion beam140 to allow more processing of this region. Similarly, regions wherelittle material is to be removed may be lightly processed by scanningthe ion beam more quickly over these regions. Alternatively, oradditionally, the duty cycle, extraction current or voltage or otheroperating parameters may be varied to allow selective processing of theworkpiece.

The workpiece 10 is then processed using this first set of processingparameters, as shown in Process 440. In certain embodiments, thisprocessing may comprise an etching process. After this etching iscompleted, an updated thickness profile of the processed workpiece isthen measured using the reflectometer 160, as shown in Process 450.

This updated thickness profile is then compared to the target thicknessprofile to generate a second material modification matrix, as shown inProcess 460. As before, this second material modification matrix may bestored in the storage element 172. The controller 170 then calculatesthe second set of processing parameters based on the second materialmodification matrix, as shown in Process 470. As shown in Process 480,the workpiece 10 is then subjected to a second processing using thesecond set of process parameters determined in Process 470. FollowingProcess 480, the workpiece 10 may have a thickness profile that issimilar to the target thickness profile, and may be removed from theplaten 150. A new workpiece may be placed on the platen 150 andProcesses 410-480 may be repeated for this new workpiece.

While FIG. 4 shows the workpiece 10 being subjected to two processes,other embodiments are also possible. For example, in certainembodiments, Processes 450-480 may be repeated multiple times for eachworkpiece to achieve improved results. In other words, the thicknessprofile of the processed workpiece may be measured a plurality of times,an updated material modification matrix may be generated based on eachmeasured thickness profile, and the workpiece may be processed based oneach updated material modification matrix.

In other embodiments, after Process 440 has been completed, thethickness profile of the workpiece 10 may be sufficiently close to thetarget thickness profile. In these embodiments, Processes 450-480 maynot be performed and the workpiece 10 may be removed from the platen 150after Process 440 is completed. In this embodiment, each workpiece mayonly undergo Processes 410-440.

While FIG. 4 is described as using an etching process, other embodimentsare also possible. For example, the etch rate profile determined inProcess 400 may also be indicative of the deposition or amorphizationrate profiles of the ion beam. Thus, the sequence shown in FIG. 2 may beused to create an etch rate profile, such as that shown in FIG. 3, whichmay then be used for subsequent deposition or amorphization processes.Thus, Process 440 and Process 480 may be deposition or amorphizationprocesses in certain embodiments.

Further, the sequence shown in FIG. 2 may be modified, in the case ofdeposition. For example, rather than directing an ion beam thatcomprises an etching species toward the workpiece, the ion beam maycomprise a deposition species. In this embodiment, rather than removingmaterial from the workpiece, the ion beam deposits material. Thedifference between the initial thickness profile, as determined inProcess 200, and the processed thickness profile, determined in Process230, would be the amount of material deposited on the workpiece as afunction of ion beam location. Thus, Process 240 would be used todetermine a deposition rate profile for the ion beam. In thisembodiment, this deposition rate profile may then be determined inProcess 400 and used throughout the sequence shown in FIG. 4. In thepresent disclosure, the rate at which the workpiece is processed due tothe ion beam, either via etching or deposition, may be referred to asthe processing rate profile. As described above, in embodiments where anetching process is performed during the sequence of FIG. 2, theprocessing rate profile is an etch rate profile. In embodiments where adeposition process is performed during the sequence of FIG. 2, theprocessing rate profile is a deposition rate profile.

FIG. 4 shows one sequence that may yield a workpiece having a thicknessprofile that is sufficiently close to a target thickness profile.However, to improve throughput, modifications to this sequence may bemade. For example, workpieces are often processed in lots. All of theworkpieces within a given lot may have properties that are very similarto one another. For example, the initial thickness profile of allworkpieces in a single lot may be very similar to one another. This maybe used to optimize the process of FIG. 4.

FIG. 5 shows one such optimization. In this sequence, the actual etchrate profile of the ion beam 140 is determined using a sacrificialworkpiece, as shown in Process 500. In other embodiments, the actualetch rate profile is determined using a workpiece to be processed. Asdescribed above, in certain embodiments, a deposition rate profile maybe determined in Process 500. Next, the initial thickness profile of thefirst workpiece of the lot is determined using the reflectometer 160.This information is used to create a first material modification matrix,as shown in Process 510, which may be stored in storage element 172.This first material modification matrix is then used by the controller170 to determine the first set of processing parameters as shown inProcess 520. Then, this first set of processing parameters is used toprocess this first workpiece, as shown in Process 530. After thisprocess is completed, the workpiece is fabricated in accordance withProcesses 450-480 of FIG. 4. In other words, the updated thicknessprofile of the processed workpiece is determined, as shown in Process450. The second material modification matrix is calculated, as shown inProcess 460, and is used to determine the second set of processingparameters, as shown in Process 470. Finally, the workpiece is processedusing the second set of processing parameters as shown in Process 480.The workpiece is then removed from the platen and a new workpiece fromthat lot is introduced.

In this embodiment, unlike that of FIG. 4, processes 510-520 are notperformed for the subsequent workpieces of the same lot. Rather, it isassumed that the initial thickness profile of each workpiece in a lot issufficiently similar so that the first workpiece can be used as thethickness model for all workpieces in that lot. Thus, all of theworkpieces of the lot are processed using the same first set ofprocessing parameters. However, in certain embodiments, each workpiecefrom that lot is processed using a unique second set of processingparameters which are determined based on the updated thickness profileof that particular workpiece. In other embodiments, each workpiece fromthat lot is processed using the same second set of processing parametersthat were determined based on the first workpiece in the lot.

Another optimization to the sequence shown in FIG. 5 is also possible.In certain embodiments, the thickness profile of the workpiecesfollowing Process 530 may be sufficiently close to the target thicknessprofile that additional processing may not be required. In theseembodiments, the workpiece may be removed from the platen after Process530 and a new workpiece may be placed on the platen. In this embodiment,Processes 510-530 are performed for the first workpiece of a lot, butonly Process 530 is performed for the subsequent workpieces of that lot.This sequence may represent the maximum throughput that may be achieved.

The embodiments described above in the present application may have manyadvantages. As described above, ion beams typically displaynon-uniformity in terms of beam current. This non-uniformity affects theprocessing rate profile that is actually achieved by different portionsof the ion beam. By measuring the actual processing rate profile of theion beam as a function of ion beam position, improved processing ofworkpieces may be achieved. Specifically, it may be possible to etchworkpieces having various thickness profiles such that the workpiece,after processing, is uniformly thick, such as within angstroms.Additionally, this technique may be applied to other processes, such asdeposition and amorphization. In addition, the present techniquemeasures the actual processing rate profile, and therefore may be moreaccurate than other methods which measure ion beam current andinterpolate etch rate profile from that measurement.

The present disclosure is not to be limited in scope by the specificembodiments described herein. Indeed, other various embodiments of andmodifications to the present disclosure, in addition to those describedherein, will be apparent to those of ordinary skill in the art from theforegoing description and accompanying drawings. Thus, such otherembodiments and modifications are intended to fall within the scope ofthe present disclosure. Furthermore, although the present disclosure hasbeen described herein in the context of a particular implementation in aparticular environment for a particular purpose, those of ordinary skillin the art will recognize that its usefulness is not limited thereto andthat the present disclosure may be beneficially implemented in anynumber of environments for any number of purposes. Accordingly, theclaims set forth below should be construed in view of the full breadthand spirit of the present disclosure as described herein.

What is claimed is:
 1. A method of processing a workpiece, comprising:measuring an initial thickness profile of a first workpiece; directingan ion beam toward the first workpiece for a predetermined time or dose;measuring an updated thickness profile of the first workpiece after thedirecting; determining an etch rate profile of the ion beam as afunction of ion beam position based on a difference between the initialthickness profile and the updated thickness profile; and processing asecond workpiece based on the etch rate profile of the ion beam.
 2. Themethod of claim 1, wherein the processing of the second workpiece isperformed using a plurality of passes, wherein the ion beam is scannedacross the second workpiece during each pass, wherein the etch rateprofile is used to determine a first set of processing parameters thatare selected from the group consisting of a number of passes, andoperating parameters used during each pass.
 3. The method of claim 2,wherein the operating parameters are selected from the group consistingof a scan speed profile, a duty cycle of the ion beam, an extractioncurrent or voltage, and a pressure of a feed gas.
 4. The method of claim1, wherein the initial thickness profile and the updated thicknessprofile are measured using a reflectometer.
 5. The method of claim 1,wherein the processing comprises an etch process, a deposition processor an amorphization process.
 6. A method of processing a workpiece,comprising: determining a processing rate profile of an ion beam as afunction of ion beam position; determining an initial thickness profileof the workpiece; using the processing rate profile, the initialthickness profile and a target thickness profile to calculate a firstset of processing parameters; and processing the workpiece using thefirst set of processing parameters.
 7. The method of claim 6, furthercomprising: determining an updated thickness profile of the workpieceafter the processing; using the processing rate profile, the updatedthickness profile and the target thickness profile to calculate a secondset of processing parameters; and processing the workpiece using thesecond set of processing parameters.
 8. The method of claim 6, whereindetermining the processing rate profile comprises: measuring an initialthickness profile of a sacrificial workpiece; directing the ion beamtoward the sacrificial workpiece for a predetermined time or dose;measuring an updated thickness profile of the sacrificial workpieceafter the directing; and determining the processing rate profile basedon a difference between the initial thickness profile and the updatedthickness profile.
 9. The method of claim 8, wherein the processing rateprofile is determined based on the predetermined time.
 10. The method ofclaim 8, wherein the ion beam removes material from the sacrificialworkpiece, and the processing rate profile comprises an etch rateprofile.
 11. The method of claim 8, wherein the ion beam depositsmaterial on the sacrificial workpiece, and the processing rate profilecomprises a deposition rate profile.
 12. The method of claim 6, whereinthe processing is performed using a plurality of passes, wherein the ionbeam is scanned across the workpiece during each pass, and wherein thefirst set of processing parameters is selected from the group consistingof a number of passes and operating parameters used during each pass.13. The method of claim 12, wherein the operating parameters areselected from the group consisting of a scan speed profile, a duty cycleof the ion beam, an extraction current or voltage, and a pressure of afeed gas.
 14. The method of claim 6, wherein the processing comprises anetch process, a deposition process or an amorphization process.
 15. Amethod of processing a plurality of workpieces from a lot, comprising:determining an etch rate profile of an ion beam as a function of ionbeam position using a sacrificial workpiece; determining an initialthickness profile of a first workpiece of the lot; using the etch rateprofile, the initial thickness profile of the first workpiece and atarget thickness profile to calculate a first set of processingparameters; processing the first workpiece of the lot using the firstset of processing parameters; and processing a second workpiece of thelot using the first set of processing parameters.
 16. The method ofclaim 15, further comprising, before processing the second workpiece:determining an updated thickness profile of the first workpiece of thelot after the processing of the first workpiece; using the etch rateprofile, the updated thickness profile of the first workpiece and thetarget thickness profile to calculate a second set of processingparameters for the first workpiece; and processing the first workpieceof the lot using the second set of processing parameters for the firstworkpiece.
 17. The method of claim 16, further comprising: determiningan updated thickness profile of the second workpiece of the lot afterprocessing the second workpiece; using the etch rate profile, theupdated thickness profile of the second workpiece and the targetthickness profile to calculate a second set of processing parameters forthe second workpiece; and processing the second workpiece of the lotusing the second set of processing parameters for the second workpiece.18. The method of claim 15, wherein determining the etch rate profilecomprises: measuring an initial thickness profile of the sacrificialworkpiece; directing the ion beam toward the sacrificial workpiece for apredetermined time or dose; measuring an updated thickness profile ofthe sacrificial workpiece after the directing; and determining the etchrate profile based on a difference between the initial thickness profileand the updated thickness profile.